Pump and motor hydraulic transmission



D. F. FROEBE 3 Sheets-Sheet 1 I PUMP AND MOTOR HYDRAULIC TRANSMISSION May 19, 1964 Filed Feb. 19, 1962 '5 Sheets-Sheet 2 INVENTOR Doz/GLA; FQOEBE May 19, 1964 D. F.. FROEBE PUMP AND MoToR HYDRAULIC TRANSMISSION Filed Feb, 19, 1962 BY R May 19, 1954 D. F. FROEBE 3,133,418

PuMxD AND MoToR HYDRAULIC TRANSMISSION Filed Feb. 19, 1962 s sheets-sheet s United States Patent O 3,133,418 PUMP AND MOTR HYDRAULEC TRANSMESSEON Douglas F. Froebe, 116 Latham St., Piedmont, Calif. Filed Feb. 19, 1962, Ser. No. 173,924 4 Claims. (Cl. dil-53) This invention relates generally to variable speed transmissions of the pump and motor hydraulic type, and is particularly directed to an improved transmission of this type embodying reduced mechanical resistance and other advantageous features contributing to greater efficiency and superior performance characteristics.

A particularly advantageous type of pump and motor hydraulic variable speed transmission is detailed in my prior U.S. Patent No. 2,569,562 which issued October 2, 1951. Basically such transmission includes a variable displacement hydraulic pump unit and a constant capacity hydraulic motor. The pump unit comprises a cylinder block fixed to and rotatable with a power input shaft. A plurality of circumferentially spaced longitudinal pump cylinders are provided in the block and a plurality of pistons are mounted for reciprocation within the respective cylinders. The hydraulic motor similarly includes a motor cylinder block having a plurality of motor 'cylinders defined therein positioned to correspond to the pump cylinders. A plurality of pistons are mounted for reciprocation in the motor cylinders while the motor block is connected to rotate with a driven shaft through a bell casing. The pump and motor blocks are disposed in coaxially spaced relation, the respective cylinders thereof being in longitudinal alignment. A stationary valve head is disposed coaxially adjacent the pump block, such valve head having separate passages arranged to communicate with the separate cylinders of the pump block during its rotation. A valve block is coaxially interposed between the stationary valve head and motor block and this valve block is carried by and rotatable with the input shaft. The valve block has a plurality of passages complementary to those of the valve head and arranged to communicate with the separate ports of the motor block during rotation thereof and of the input shaft. The valve head is additionally provided with ducts through which liquid flows between the separate passages of the valve head and valve means are provided in the ducts to control such ow and selectively engage or disengage fluid coupling between the pump and motor units. With the foregoing arrangement, liuid coupling between the pump and motor blocks, and therefore between the input and driven shafts may be varied through a wide range of speed ratios which depend upon the relative phase between the strokes of the pump and motor pistons, To control such relative phase a variably positionable swash plate is provided in bearing relation to the heads of the pump pistons which are spring loaded in the direction of the plate. The swash plate is operable to swing in an arcuate path centered about an axis transverse to the drive shaft whereby the strokes of the pump pistons are varied in accordance with the inclination of the plate. The strokes of the motor pistons are invariably set by a fixed angle swash plate secured to the input shaft and bearing against the heads of the motor pistons, also serving as a thrust linkage between the input shaft, motor pistons and motor block. Thus as the input shaft rotates, the relative phase between the strokes of the pump and motor pistons may be varied by changing the inclination of the variably positionable swash plate to in turn change the speed ratio. For further details of the previously outlined transmission, reference may be had to the hereinbefore referenced patent.

I have found that marked improvements in the efficiency and operational characteristics of the transmission generally outlined above are derived by incorporation of several structural modifications therein. Principally I ice have found that the mechanical resistance occurring between the pistons and cylinder walls as well as elsewhere in the previous transmission structure may be materially minimized. More particularly, the tubular spring returned pistons utilized in the prior transmission are subject to excessive resistance due to the internal hydraulic pressure created within the cylinders. In addition, the swash plates in bearing against the piston heads represent additional sources of mechanical resistance in the prior device. In accordance with the present invention improved piston and piston stroke control and thrust linkage assemblies are provided in the pump and motor units to the end of minimizing mechanical resistance. In addition, provision is made to minimize increased friction resistance at the seal surfaces between the fixed valve head and the valve block carried by the input shaft, and between the valve block and motor block due to any misalignment of truth between the input shaft and seal surfaces.

It is therefore an object of the present invention to proivide in a transmission of the type referred to, minimized mechanical resistance with an attendant increase in efiiciency and performance characteristics.

Another object of the invention is to provide a transmission of the class described wherein flat top pistons are employed in conjunction with a direct connection stroke control linkage and thrust linkage of novel design having comparatively low mechanical resistance characteristics.

Still another object of the invention is the provision of resiiient mounting means in a transmission of the class described which automatically compensates for any misalignment or out of trueness between the input shaft and seal surfaces between the fixed valve head and rotary valve block and between the valve block and motor block.

It isla further object of the invention to provide dynamic balance means in direct connection piston stroke control and thrust linkage of the type referred to.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawings and description may be adopted Within the scope of the invention as set forth in the claims.

`FIGURE 1 is a vertical sectional view taken longitudinally of the improved transmission in accordance with the present invention.

`FIGURE 2 is a sectional view taken at line y2 2 of FIGURE 1.

FIGURE 3 is la vertical sectional view of the piston stroke control mechanism employed in the pump unit transmission.

FIGURE 4 is a sectional view taken at line 4-4 of FIGURE 1, illustrating particularly further details of the pump unit piston `stroke control mechanism.

FIGURE 5 is a sectional view taken at line 5 5 of FIGURE l, illustrating the piston stroke regulating mechanism of the motor unit of the transmission and the dynamic balancing means employed in such unit.

Referring now to the drawings, FIGURES 1 and 2 in particular, l1 designates a pump and motor hydraulic transmission of the general type disclosed in my prior U.S. Patent No. 2,569,562. The transmission includes a variable displacement hydraulic pump unit 12 and a constantl capacity hydraulic motor unit 13. The pump unit comprises a pump cylinder block 14- splined or keyed to an input power shaft i6 so as to be rotatable therewith. The block 14 is disposed within an outer casing 17 with the input shaft being journalled with one end of the casing and with .a bell housing 18 concentrically chi) rotatably mounted within the opposite end of the casing. A plurality of pistons 19 are mounted for reciprocation within a corresponding plurality of circumferentially spaced longitudinally pump cylinders 21 ofthe block 14.l

The motor unit 13 includes a motor cylinder block 22, similar in form to the pump block 14, coaxially end secured to the bell housing 18 for rotation therewith, rotation of the motor block being thus transmitted to an output shaft 23 projecting axially from the bell housing and transpiercing the end of the casing 17. In order that the motor block revolve upon the input shaft lo extending coaxially therethrough a suitable bearing 24 is conoentrically interposed therebetween. The motor block 22 is provided with a plurality of motor cylinders 26 similar in position and number to the pump cylinders 21. A plurality of pistons 27 are respectively reciprocably mounted within the cylinders 26.

A valve head 2S is iixedly secured within the casing 17 and centrally transpierced by the input shaft 16, a suitable bearing 29 being concentrically disposed between the head and shaft to facilitate relatively free rotation of the latter. The valve head is formed with intake and discharge por-ts having continuing ducts 3d which connect with arcuate collector channels 31 whose center of curvature coincides with the axis of the input shaft and which are open along their length at the face of the head which bears against the pump cylinder block The intake ports of the valve head are in confronting relation to ports of .the pump cylinders 21.

A second valve head 32 generally similar to valve head 2S is keyed, splined, or otherwise iixedly secured to the input shaft 16 in coaxially interposed relation to the valve head 28 and motor block 22. The valve head 32 is likewise formed with intake and discharge ports opening into arcuate collector channels 33, the latter collector channels being in confronting relation to channels 3@ and defining enclosed collector chambers therewith. The intake and discharge ports of valve nead 32 are registerable with the ports of 4the valve head 28 and ports of the motor cylinders Z6. The respective cylinders of the pump and motor units are thus in communication with each other through the valve heads 2S, 32.

The fixed valve head 25 is provided with an integral downwardly extending portion 341 immersed in the supply of liuid which tills the lower portion of the casing 17, the extension having vertical passages 35 therein communieating at their upper ends with the chambers delined by collector channels 3), 33. In addition valve means 37 are provided in communication with passages 36 to control the tlow of fluid therethrough. Inasmuch as the valve means 37 has no bearing upon the improvements of the instant invention, a detailed description of the valve means is not included herein, reference being made to my previously referenced prior patent for such description.

ln `transmissions of the type outlined hereinbefore, variation in the speed ratios between the input and output `shafts are facilitated by `a suitable thrust linkage coupled between the input shaft and motor pistons and a control mechanism for controlling the relative phase between the strokes of the pump pistons and motor pistons. Through control of such relative phase the pressure ow of fluid between the pump and motor cylinders is varied to effect a corresponding control over the thrust imparted to the motor cylinder block through the pistons and thrust linkage and therefore to the output shaft. A detailed explanation of the manner in which control of the relative phase between the strokes of the pump and motor pistons effects variations in speed ratio is found in my prior Patent No. 2,569,552 and accordingly not included herein.

As noted previously, the piston stroke phase control means and the thrust linkage employed heretofore included a lixed angle swash plate keyed or otherwise tixed to the input shaft and disposed to be engageable with the heads of the motor pistons. In addition, a variably positionable swash plate was provided pivoted to the outer casing and bearing against the heads of the pump pistons. Both the pump and motor pistons were tubular with rounded heads and disposed with their sleeve ends in the pump and motor blocks. Such pistons were spring loaded in the `directions of the swash plates. By selectively varying the inclination `of the variably positionable swash plate the relative phase between the strokes of the pump and motor pistons could thus be varied. The prior pistons and awash plate control mechanism and thrust linkage employed in the transmission have since been `found to be subject to improvement, particularly to the end of decreasing the mechanical resistance attending same.

In accordance with the present invention a low mechanical resistance piston, stroke phase control mechanisrn, and thrust linkage are employed in the transmission 11. More particularly, it is to be noted that the pump pistons 19 an dmotor pistons 27 are tubular and formed with flat inner end faces 38, 39, viz., tiat faces at the ends disposed adjacent the inner ends of the cylinders. I have found that minimized mechanical resistance due to the internal hydraulic pressure within the cylinders arises from employment of pistons having the foregoing configuration.

in order to actuate the pistons and control their strokes, an improved stroke control mechanism 41 and thrust linkage ft2 are employed therewith. The control mechanisrn 41 and linkage 42 include ball end piston rods 43, 44 respectively connected in actuating relation to the pump and motor pistons 19 and 27. The rods 43, 44 project longitudinally exteriorly from the cylinders to be connected at their outer ends to stroker bearing plates 46, 47. The plate 46 is pivotally mounted within outer casing 17 so as to be selectively variable in inclination about an axis transverse to the axis of the input shaft 16. In addition the plate 46 is arranged to be rotatable with the pump block, preferably by universal mounting means 4S coupling the plate to the input shaft. Plate 47 is mounted at a fixed angle upon the input shaft and arranged to be rotatable with the motor block 22, preferably by universal mounting means 49 coupling the plate to the bell housing 18. lt will be thus appreciated that as the inclination of the stroker plate 46 is varied the phase of the strokes of the pump pistons are varied relative to the fixed phase of the strokes of the motor pistons set by Stroker plate 7. Such variations in phase produces a corresponding variation in thrust imparted to the motor block through the plate i7 and motor pistons in a similar manner to that occurring due to the swash plate control mechanism and thrust linkage disclosed in my prior patent.

Considering now the Stroker plates 46, 47 in greater detail, it is iirst to be noted that the plates are annular and respectively provided with pluralities of circumferentially spaced ball sockets 51 and S2. The sockets receive the exterior ball ends of the piston rods 43, 44, the interior ball ends of the rods being received in ball sockets 53, 5d formed in the pistons 19, 27. Plate 45 is carried concentrically within a mounting carriage 56 including an annular carriage plate 57 pivotally secured to the outer casing for rotation about a transverse axis by means of transversely diametrically opposed spindles 58. The Stroker plate is rotatable Within the carriage plate 57. The universal mounting means 48 for coupling the Stroker plate to the input shaft to effect the rotation of the former preferably includes a collar 59, keyed, splined or otherwise ixedly secured to the input shaft as best shown in FIGURE 4. An annular insert 61 is concentrically interposed between the collar 59 and stroker plate, a pair of diametrically opposed spindles 62 being rigidly secured to the collar and pivotally secured to the insert. The insert in turn carries diametrically opposed spindles 65 rotatably mounted therein at positions displaced 90 from spindles 62 and rigidly secured to the stroker plate.

It will thus be appreciated that the mounting means 48 permits universal movement of the Stroker plate 46 during its rotation by the input Shaft.

As regards the Stroker plate 47, it is to be noted, as best shown in FIGURE 5, that Same is keyed, splined, or otherwise rigidly secured at a iixed angle to the input shaft 16. The universal mounting means 49 preferably comprises an annular insert 64 concentrically interposed between Stroker plate 47 and bell housing 18. A pair of diametrically opposed spindles 66 are rigidly secured to the Stroker plate and rotatably mounted in the insert 64. A second pair of diametrically opposed spindles 67 displaced 90 from spindles 66 are similarly rotatably mounted in the insert and rigidly secured to the bell housing. Hence universal movement of the Stroker plate 47 relative to the bell housing during rotation of the former is facilitated by the mounting means 49.

It is of importance to note the manner in which the Stroker plate 47 is dynamically balanced. In this regard it should be noted that the plate is attached to a hub 68 xedlysecured to the input shaft, the hub projecting oppositely from the inclined Stroker plate. Diametrically opposed balance weights 69, 71 are secured to the oppositely projecting ends of the hub in counteracting relation to the offset plane of the plate, thus dynamically balancing same.

To facilitate the ready adjustment of the inclination of the variably positionable strokes plate 46, a power assist control mechanism 72 is provided as best Shown in FIGURE 3. The control mechanism 72 is substantially similar to that disclosed in detail in my prior Patent No. 2,569,562. Generally, the mechanism 72 includes a hydraulic cylinder 73 having ports 74 at its opposite ends. A piston 76 is reciprocably mounted within cylinder 73 and iS coupled through a linkage 77 to the Stroker plate carriage 56 to effect pivoting thereof to varied inclined positions. A hydraulically balanced control valve 78 regulates the amount of hydraulic fluid drawn from the pressure System of the transmission as supplied by pressure strokes of the pumping unit and entering the cylinder ports 74. A manually operable control lever 79 coupled to linkage 77 facilitates movement of the control valve 78 and therefore of the piston 76 to Vary the setting of the Stroker plate 46.

As mentioned previously, the sealing surfaces between the opposite faces of the valve block 32 and respectively the valve head 2S and motor block 22 if misaligned with the input shaft 16 or out-of-trueness contribute to the over-all mechanical resistance of the transmission. Accordingly, in order to overcome this disadvantage, and as a particularly important adjunct of the invention suitable resilient mounting means are provided to compensate for such misalignment or out-of-trueness. More particularly it Will be noted that resilient sleeves 81, S2 of rubber or the like are respectively interposed between bearing 29 and the valve head 2S and between bearing 24 and the motor block 22. By virtue of the resiliency of the sleeves, the valve head and motor block automatically position themselves in proper trueism with the faces of the valve block 32 and in sutiable alignment with the input shaft.

What is claimed is:

l. In a pump and motor hydraulic transmission of the type including rotatable separate input and output shafts, a multi-cylinder fixed capacity motor unit operatively disposed between said input and output shafts and having relatively confronting ports through which liquid may be transferred between the cylinders of said pump and motor units, a fixed valve head having separate passages therein arranged to communicate with ports of the pump unit during rotation of the latter, a valve block carried by and rotatable with the input shaft and provided with separate passages complementary with the passages of the valve head and arranged to communicate with the ports of the motor unit during rotation of the latter and of the input shaft, said valve head having therein ducts through which iluid flows between the separate passages of said valve head, pistons reciprocably mounted within the cylinders of said pump and motor units, and a bell housing connecting said motor unit to said output shaft, the irnprovement comprising a variably positionable Stroker plate operative with said pump unit and rotatable therewith, universal mounting means connecting said Stroker plate to Said input shaft, ball ended piston rods connecting the pistons of said pump unit to said Stroker plate, a fixed angle Stroker plate operative with said motor unit and output shaft and maintained at a fixed angle to said input shaft, second universal mounting 4means connecting Said fixed angle Stroker plate to said bell housing, and ball ended piston rods connecting the pistons of said motor unit to said fixed angle Stroker plate, said variably positionable Stroker plate controlling the volume of successive admissions and discharges of liquid to and from its associated pump unit during rotation of the input shaft and said xed angle Stroker plate governing relative rotation of said output shaft relative to said input shaft in proportion to transfer of liquid between the pump and motor umts.

2. Apparatus according to claim l, further defined by Said variably positionabie Stroker plate being concentrically rotatably disposed within an annular carriage plate, said carriage plate being povitally mounted for movement about an axis transverse to the axis of said input Shaft; said first universal mounting means comprising a collar xedly secured to said input shaft, an annular insert concentrically interposed between said collar and insert, means pivotally mounting Said insert for movement about a diametric axis relative to said collar, and means pivotally mounting Said insert for movement relative to said carriage plate about a second diametric axis displaced from said first diametric axis; an-d said second universal mounting means comprising an annular insert concentrically interposed between said fixed angle Stroker plate and said bell housing, means pivotally mounting said insert for movement about a diametric axis relative to said fixed angle Stroker plate, and means pivotally mounting said insert for movement relative to said bell housing about a second diametric axis displaced 90 from the rst diametric axis.

3. Apparatus according to claim 2, further defined by bearings concentrically interposed between said valve head and input shaft and between said motor unit and said input shaft, and resilient sleeves concentrically interposed and secured between said bearings and valve head and motor unit.

4. -In a pump and motor hydraulic transmission of the type including rotatable separate input and output shafts, a multi-cylinder variable capacity pump unit connected for rotation with said input shaft, a multi-cylinder yfixed capacity motor unit operatively disposed between said input and output shafts and having relatively confronting ports through which liquid may be transferred between the cylinders of said pump and motor units, a fixed valve head having separate passages therein arranged to communicate with ports of the pump unit during rotation of the latter, and a valve block carried by and rotatable with the input shaft and provided with separate passages complementary with the passages of the valve head and arranged to communicte with the ports of the motor unit during rotation of the latter and of the input shaft, said valve head having therein ducts through which fluid flows between the separate passages of said valve head, the improvement comprising resilient mounting means securing said valve head and said motor unit to said input shaft.

References Cited in the tile of this patent UNITED STATES PATENTS 

4. IN A PUMP AND MOTOR HYDRAULIC TRANSMISSION OF THE TYPE INCLUDING ROTABLE SEPARATE INPUT AND OUTPUT SHAFTS, A MULTI-CYLINDER VARIABLE CAPACITY PUMP UNIT CONNECTED FOR ROTATION WITH SAID INPUT SHAFT, A MULTI-CYLINDER FIXED CAPACITY MOTOR UNIT OPERATIVELY DISPOSED BETWEEN SAID INPUT AND OUTPUT SHAFTS AND HAVING RELATIVELY CONFRONTING PORTS THROUGH WHICH LIQUID MAY BE TRANSFERRED BETWEEN THE CYLINDERS OF SAID PUMP AND MOTOR UNITS, A FIXED VALVE HEAD HAVING SEPARATE PASSAGES THEREIN ARRANGED TO COMMUNICATE WITH PORTS OF THE PUMP UNIT DURING ROTATION OF THE LATTER, AND A VALVE BLOCK CARRIED BY AND ROTATABLE WITH THE INPUT SHAFT AND PROVIDED WITH SEPARATE PASSAGES COMPLEMENTARY WITH THE PASSAGES OF THE VALVE HEAD AND ARRANGED TO COMMUNICATE WITH THE PORTS OF THE MOTOR UNIT DURING ROTATION OF THE LATTER AND OF THE INPUT SHAFT, SAID VALVE HEAD HAVING THEREIN DUCTS THROUGH WHICH FLUID FLOWS BETWEEN THE SEPARATE PASSAGES OF SAID VALVE HEAD, THE IMPROVEMENT COMPRISING RESILIENT MOUNTING MEANS SECURING SAID VALVE HEAD AND SAID MOTOR UNIT TO SAID INPUT SHAFT. 